Harald Höger

Medical University of Vienna, Wien, Vienna, Austria

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Publications (169)641.85 Total impact

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    ABSTRACT: Several neurotransmitter receptors have been proposed to be involved in memory formation. However, information on receptor complexes (RCs) in the radial arm maze (RAM) is missing. It was therefore the aim of this study to determine major neurotransmitter RCs levels that are modulated by RAM training because receptors are known to work in homo-or heteromeric assemblies. Immediate early gene Arc expression was determined by immunohistochemistry to show if prefrontal cortices (PFC) and hippocampi were activated following RAM training as these regions are known to be mainly implicated in spatial memory. Twelve rats per group, trained and untrained in the twelve arm RAM were used, frontal cortices and hippocampi were taken, RCs in membrane protein were quantified by blue-native PAGE immunoblotting. RCs components were characterised by co-immunoprecipitation followed by mass spectrometrical analysis and by the use of the proximity ligation assay. Arc expression was significantly higher in PFC of trained as compared to untrained rats whereas it was comparable in hippocampi. Frontal cortical levels of RCs containing AMPA receptors GluA1, GluA2, NMDA receptors GluN1 and GluN2A, dopamine receptor D1, acetylcholine nicotinic receptor alpha 7 (nAChR-α7) and hippocampal levels of RCs containing D1, GluN1, GluN2B and nAChR-α7 were increased in the trained group; phosphorylated dopamine transporter levels were decreased in the trained group. D1 and GluN1 receptors were shown to be in the same complex. Taken together, distinct RCs were paralleling performance in the RAM which is relevant for interpretation of previous and design of future work on RCs in memory studies. Copyright © 2015. Published by Elsevier B.V.
    Behavioural brain research 04/2015; 289. DOI:10.1016/j.bbr.2015.04.043 · 3.39 Impact Factor
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    ABSTRACT: Drebrin (DBN), an actin-bundling key regulator of dendritic spine genesis and morphology, has been recently proposed as a regulator of hippocampal glutamatergic activity which is critical for memory formation and maintenance. Here, we examined the effects of genetic deletion of DBN on dendritic spine and on the level of complexes containing major brain receptors. To this end, homozygous and heterozygous DBN knockout mice generated in our laboratory and related wild type control animals were studied. Level of protein complexes containing dopamine receptor D1 (D1R)/dopamine receptor D2 (D2R), 5-hydroxytryptamine receptor 1A (5-HT1A R) and 5-hydroxytryptamine receptor 7 (5-HT7R) were significantly reduced in hippocampus of DBN knockout mice whereas no significant changes were detected for GluR1, 2 and 3 and NR1 as examined by native gel-based immunoblotting. DBN depletion also altered dendritic spine formation, morphology and reduced levels of D1R in dendritic spines as evaluated using immunohistochemistry/confocal microscopy. Electrophysiological studies further showed significant reduction in memory-related hippocampal synaptic plasticity upon DBN depletion. These findings provide unprecedented experimental support for a role of DBN in the regulation of memory-related synaptic plasticity and neurotransmitter receptor signalling, offer relevant information regarding the interpretation of previous studies and help in the design of future studies on dendritic spines. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Journal of Neurochemistry 04/2015; DOI:10.1111/jnc.13119 · 4.24 Impact Factor
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    ABSTRACT: AMPA receptors (AMPARs; alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) are glutamate-gated ion channels that mediate the majority of fast excitatory synaptic transmissions in the mammalian brain. A series of phosphorylation sites have been predicted or identified and knowledge on phosphorylations is mandatory for understanding receptor biology and functions. Immunoprecipitation from extracted hippocampal rat proteins was carried out using an antibody against the AMPAR GluA1 subunit, followed by identification of GluA1 and binding partners by mass spectrometry. Bands from SDS-PAGE were picked, peptides were generated by trypsin and chymotrypsin digestion and identified by tandem mass spectrometry (LTQ Orbitrap Velos). Using Mascot as a search engine, phosphorylation sites S506, S645, S720, S849, S863, S895, T858, Y228, Y419 and T734 were found on GluA1; S357, S513, S656, S727, T243, T420, T741, Y 143, Y301,Y426 on GluA2; S301, S516, S657, S732, T222 and T746 were observed on GluA3 and S514, S653 was phosphorylated on GluA4. A series of additional protein modifications were observed and in particular, tyrosine and tryptophan nitrations on GluA1 were detected that may raise questions on additional regulation mechanisms for AMPARRs in addition to phosphorylations. The findings are relevant for interpretation of previous work and design of future studies using AMPAR serving as a resource for neuroscience research and indeed, phosphorylations and PTMs per se would have to be respected when neuropathological and neurological disorders are being studied. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Proteomics. Clinical applications 02/2015; DOI:10.1002/prca.201400057 · 2.68 Impact Factor
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    ABSTRACT: Proteoglycans (PGs) are major constituents of the extracellular matrix and have recently been proposed to contribute to synaptic plasticity. Hippocampal PGs have not yet been studied or linked to memory. The aim of the study therefore was to isolate and characterize rat hippocampal PGs and determine their possible role in spatial memory. PGs were extracted from rat hippocampi by anion exchange chromatography and analysed by nano LC-MS/MS. 20 male Sprague-Dawley rats were tested in the Morris Water Maze (MWM). PGs agrin, amyloid beta A4 protein, brevican, glypican-1, neurocan, phosphacan, syndecan-4, and versican were identified in the hippocampi. Brevican and versican levels in the membrane fraction were higher in the trained group, correlating with the time spent in the target quadrant. AMPA receptor GluR1 was co-precipitated with brevican and versican. Levels for a receptor complex containing GluR1 was higher in trained while GluR2 and GluR3-containing complex levels were higher in yoked rats. The findings provide information about the PGs present in the rat hippocampus, demonstrating that versican and brevican are linked to memory retrieval in the MWM and that PGs interact with AMPA receptor GluR1, which is linked to memory retrieval. This article is protected by copyright. All rights reserved.
    Journal of Neurochemistry 06/2014; 130(6). DOI:10.1111/jnc.12783 · 4.24 Impact Factor
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    ABSTRACT: The link between the cholinergic and serotonergic system in cognitive function is well-documented. There is, however, limited information on spatial memory and this formed the rationale to carry out a study with the aim to show a specific link between nicotinic and serotonergic receptor complexes rather than the corresponding subunits, to spatial memory retrieval in a land maze. A total of 46 mice were used and divided into two groups, trained and untrained (yoked) in the Multiple-T-Maze (MTM) and following training during the first four days, probe trials for memory retrieval were performed on days 8, 16 and 30. Six hours following scarification, hippocampi were taken for the analysis of native receptor complex levels using blue-native gels followed by immunoblotting with specific antibodies.5-HT1A-, 5-HT7-, nAChα4- and nACh-α7-containing receptor complexes were observed and were paralleling memory retrievals and receptor complex levels were shown to be significantly different between trained and yoked animals. Only levels of a nicotinic acetylcholine α7 receptor-containing complex at an apparent molecular weight of approximately 480kDa were shown to be linked to memory retrieval on day 8 but not to retrievals on days 16 and 30 when memory extinction has taken place. Correlation between nAChα4-, 5-HT1A- and 5-HT7-containing receptors and latencies on day 16 may point to a probable link in extinction mechanisms. A series of the abovementioned receptor complexes were correlating among each other probably indicating a serotonergic/cholinergic network paralleling spatial memory formation.
    Behavioural Brain Research 05/2014; 270. DOI:10.1016/j.bbr.2014.05.012 · 3.39 Impact Factor
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    ABSTRACT: Although a large series of reports on monoamine receptor (MAR) biochemistry and pharmacology in aging are available, work on MAR complexes rather than subunits is limited. It was the aim of the study to determine MAR complexes in hippocampi of three different age groups (3-12 and 18 months) in the mouse and to link MAR changes to spatial memory retrieval in the Morris Water Maze (MWM). MAR complexes were separated by blue native electrophoresis. Immunohistochemistry was performed in order to show the pattern of dopamine receptors and its colocalisations. D1R, D2R and 5-HT7R containing receptor complex levels were decreasing with age while 5-HT1AR-containing complex levels were increasing with age. D1R, 5-HT7R and 5-HT1AR were significantly correlating with the time spent in the target quadrant, representing retrieval in the MWM. D1R and D2R immunoreactivity was decreasing in an area-dependent pattern and D1R and D2R were colocalised. Individual monoamine receptors are linked to spatial memory retrieval and are modulated by age. The findings are relevant for interpretation of previous and design of future work on brain receptors, spatial memory and aging.
    Behavioural brain research 02/2014; 264. DOI:10.1016/j.bbr.2014.01.042 · 3.39 Impact Factor
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    ABSTRACT: Although a few individual members of the protein kinase C (PKC) family were studied in spatial memory no systematic approach was carried out to concomitantly determine all described PKC family members in spatial memory of the mouse. It was therefore the aim of the current study to link hippocampal PKCs to memory retrieval in the Morris water maze (MWM). CD1 mice were trained (n=9) or untrained (n=9) in the MWM, hippocampi were taken 6h following the test for memory retrieval and PKCs were determined in mouse hippocampi by immunoblotting. The trained animals learned the spatial memory task and kept memory at the probe trial. PKCs alpha and epsilon were comparable between groups while PKCs beta, delta, gamma (two forms, i.e. two bands on Western blotting), zeta (2 forms) were higher in trained mice and theta (2 forms) were lower in trained mice. PKC gamma (1 form) was significantly correlating with the time spent in the target quadrant (r=0.7933; P=0.0188). Changes of hippocampal levels of PKCs beta, delta, gamma, zeta and theta were paralleling memory retrieval of the MWM task but correlations revealed that spatial memory retrieval was only linked to one form of PKC gamma. Results are also in agreement with a recent publication showing that PKM zeta is not required for memory formation. These findings may be relevant for the interpretation of previous work and the design of future work on the protein kinase C family in spatial memory of the mouse.
    Behavioural brain research 09/2013; 258. DOI:10.1016/j.bbr.2013.09.039 · 3.39 Impact Factor
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    ABSTRACT: Neuronal circuitries in the hippocampus are involved in navigation and memory and are controlled by major networks of GABAergic interneurons. Parvalbumin (PV)-expressing interneurons in the dentate gyrus (DG) are identified as fast-spiking cells, playing a crucial role in network oscillation and synchrony. The inhibitory modulation of these interneurons is thought to be mediated mainly through GABAA receptors, the major inhibitory neurotransmitter receptors in the brain. Here we show that all PV-positive interneurons in the granular/subgranular layer (GL/SGL) of the mouse DG express high levels of the GABAA receptor δ subunit. PV-containing interneurons in the hilus and the molecular layer, however, express the δ subunit to a lower extent. Only 8% of the somatostatin-containing interneurons express the δ subunit, whereas calbindin- or calretinin-containing interneurons in the DG seem not to express the GABAA receptor δ subunit at all. Hence, these cells receive a GABAergic control different from that of PV-containing interneurons in the GL/SGL. Experiments investigating a possible co-expression of GABAA receptor α1, α2, α3, α4, α5, β1, β2, β3, or γ2 subunits with PV and δ subunits indicated that α1 and β2 subunits are co-expressed with δ subunits along the extrasynaptic membranes of PV-interneurons. These results suggest a robust tonic GABAergic control of PV-containing interneurons in the GL/SGL of the DG via δ subunit-containing receptors. Our data are important for better understanding the neuronal circuitries in the DG and the role of specific cell types under pathological conditions.
    Neuroscience 09/2013; 254. DOI:10.1016/j.neuroscience.2013.09.019 · 3.33 Impact Factor
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    ABSTRACT: Protein phosphorylation and dephosphorylation events play a key role in memory formation and various protein kinases and phosphatases have been firmly associated with memory performance. Here, we determined expression changes of protein kinases and phosphatases following retrieval of spatial memory in CD1 mice in a Morris Water Maze task, using antibody microarrays and confirmatory Western blot. Comparing changes following single and consecutive retrieval, we identified stably and differentially expressed kinases, some of which have never been implicated before in memory functions. Based on these findings we define a small signalling network associated with spatial memory retrieval. Moreover, we describe differential regulation and correlation of expression levels with behavioural performance of polo-like kinase 1. Together with its recently observed genetic association to autism-spectrum disorders our data suggest a role of this kinase in balancing preservation and flexibility of learned behaviour. © 2013 Wiley Periodicals, Inc.
    Hippocampus 08/2013; 23(8). DOI:10.1002/hipo.22127 · 4.30 Impact Factor
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    ABSTRACT: Although a series of amino acid analogues have been shown to modulate brain function, information on the pharmacology of alpha-alkylated amino acids (AAAA) is limited. In particular there is no information on the effect of these amino acid analogues (AAA) on the elevated plus maze, the tail suspension test and the forced swim test. It was therefore the aim of the study to test a series of AAAA in these paradigms in order to explore behavioral activities of this compound class. 10 male mice per group aged between 10-14 weeks were used. Vehicle-treated controls were used in addition to intraperitoneal injections of 1, 10 and 100mg/kg body weight of each, alpha-amino-isobutyic acid (AIB), isovaline (IVA), alpha-propyl-alanine (APA), alpha-butyl-alanine (ABA), alpha-pentyl-alanine (APnA), alpha-ethylphenylglycine (AEPG) and alpha-methyl-valine (AMV). The elevated plus maze (EPM), the tail suspension test (TST) and forced swim test (FST) were used for behavioral testing. There were dose-dependent results: all compounds increased time and pathlength in the open arm of the EPM at least at one dose administered. In the TST and in the FST only the 100mg dose was showing an effect. The results show pharmacological activity modifying the EPM in low doses suggesting the use in treatment of behavioral traits and symptoms represented by or linked to the EPM including anxiety-related behaviour including depression. Compounds acting at higher doses may be used to induce behavioral changes and thus serve as neurobiological-neuropharmacological tools.
    Behavioural brain research 06/2013; DOI:10.1016/j.bbr.2013.06.008 · 3.39 Impact Factor
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    ABSTRACT: Although a series of amino acids (AA) have been associated with spatial memory formation, there is limited information on concentrations of beta-alanine and citrulline in rodent brains. Given the importance of AA metabolism in cognitive functions it was the aim of the study to determine hippocampal levels of beta-alanine and citrulline in rats during two different phases of memory retrieval in a spatial memory paradigm. Ten rats were used per group and the first group was trained and sacrificed five min, the second six hours following retrieval in the Morris Water Maze (MWM) and the third and fourth group were untrained, yoked controls. Hippocampi were taken and free AA were determined using a well-established HPLC protocol. Beta-alanine and citrulline levels were higher in trained rat hippocampi, during both, early and late phase of memory retrieval. Taurine, methionine, cysteine, lysine and ornithine levels were higher in yoked rats at the late phase while tyrosine was higher in yoked rats during the early phase. There were no significant correlations between time spent in the target quadrant and any of the AA levels. Herein, an AA pattern, different between yoked and trained animals at early and late phase of memory retrieval is shown, indicating probable involvement of different AA pathways in animals trained and untrained in the MWM. The results may be useful for the interpretation of previous studies and the design of future experiments to identify amino acids as possible targets for modulating spatial memory.
    Behavioural brain research 04/2013; 249. DOI:10.1016/j.bbr.2013.04.033 · 3.39 Impact Factor
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    ABSTRACT: The lymphocyte-specific protein tyrosine kinase (Lck), which belongs to the Src kinase-family, is expressed in neurons of the hippocampus, a structure critical for learning and memory. Recent evidence demonstrated a significant downregulation of Lck in Alzheimer's disease. Lck has additionally been proposed to be a risk factor for Alzheimer's disease, thus suggesting the involvement of Lck in memory function. The neuronal role of Lck, however, and its involvement in learning and memory remain largely unexplored. Here, in vitro electrophysiology, confocal microscopy, and molecular, pharmacological, genetic and biochemical techniques were combined with in vivo behavioral approaches to examine the role of Lck in the mouse hippocampus. Specific pharmacological inhibition and genetic silencing indicated the involvement of Lck in the regulation of neuritic outgrowth. In the functional pre-established synaptic networks that were examined electrophysiologically, specific Lck-inhibition also selectively impaired the long-term hippocampal synaptic plasticity without affecting spontaneous excitatory synaptic transmission or short-term synaptic potentiation. The selective inhibition of Lck also significantly altered hippocampus-dependent spatial learning and memory in vivo. These data provide the basis for the functional characterization of brain Lck, describing the importance of Lck as a critical regulator of both neuronal morphology and in vivo long-term memory.
    Cellular and Molecular Life Sciences CMLS 09/2012; DOI:10.1007/s00018-012-1168-1 · 5.86 Impact Factor
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    ABSTRACT: Hereditary and sporadic medullary thyroid carcinoma (MTC) are closely associated with RET proto-oncogene mutations. However, the role of additional changes in the tumor genomes remains unclear. Our objective was the identification of chromosomal regions involved in MTC tumorigenesis and to assess their significance by using MTC-derived cell lines. We used array-CGH (comparative genomic hybridization) to map chromosomal imbalances in 52 primary tumors and ten metastases. Eleven tumors (11/52, 21%) were hereditary and 41 (41/52, 79%) were sporadic. Among the latter, 15 tumors (15/41, 37%) harbored RET mutations. Furthermore, we characterized five MTC cell lines in detail and evaluated the tumorigenicity by severe combined immunodeficiency (SCID)-mouse experiments. Most MTCs had only few copy number changes, and losses of chromosomes 1p, 4q, 19p and 22q were observed most frequently. The number of chromosomal aberrations increased in metastases. Twenty-three percent (12/52) of the primary tumors did not even show any chromosomal gains and losses. We injected three cell lines (two of these were without chromosomal changes and pathogenic RET mutations) into immune deficient SCID mice, and in each case, we observed rapid tumor growth at the injection sites. Our data suggest that MTCs--in contrast to most other tumor entities--do not acquire a multitude of genomic imbalances. SCID mouse experiments performed with chromosomally normal cell lines and without RET mutations suggest that presently unknown submicroscopic genomic changes are sufficient in MTC tumorigenesis.
    International Journal of Cancer 07/2012; 131(2):E66-73. DOI:10.1002/ijc.26494 · 5.01 Impact Factor
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    ABSTRACT: Although the sodium/potassium transporting ATPase subunit alpha-3 (AT1A3) has been linked to memory mechanisms in rodents, regulation of this ATPase in terms of activity and complex levels by memory performance in a land maze has not been shown so far. It was therefore the aim of the study to link memory retrieval in the multiple T-Maze (MTM) to AT1A3 protein levels and activity. C57BL/6J mice were trained in the MTM and euthanized 6h following memory retrieval. Hippocampal membrane proteins were prepared by ultracentrifugation and run on blue native gel electrophoresis (BN-PAGE). Enzyme activity was evaluated using an in-gel method. AT1A3 protein was characterized using mass spectrometry (nano-LC-ESI-MS/MS). On BN-PAGE a single band was observed at 240kDa, which corresponds to the dimeric form of the enzyme. Higher levels of AT1A3 complex were seen in trained mice. Also ATPase activity was higher in trained mice, and was observed both at 110 and at 240kDa. Mass spectrometry unambiguously identified AT1A3 with 98.91% sequence coverage. A series of novel AT1A3 phosphorylation sites were detected. Taken together, it was shown that increased AT1A3 protein levels for the dimer as well as AT1A3 activity represented by the monomer and the dimer were paralleling memory training in the MTM. This may be relevant for understanding the role of the catalytic hydrolysis of ATP coupled with the exchange of sodium and potassium ions across the plasma membrane that generates the electrochemical gradient of sodium and potassium ions. Herein, we provide evidence for a possible role of AT1A3 in memory mechanisms and support previous findings using different animal models for memory formation.
    Neurochemistry International 07/2012; 61(5):702-12. DOI:10.1016/j.neuint.2012.07.006 · 2.65 Impact Factor
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    ABSTRACT: Modafinil has been shown to modify behavioural and cognitive functions and to effect several brain receptors. Effects, however, were not observed at the receptor protein complex level and it was therefore the aim of the study to train mice in the multiple T-Maze (MTM) as a paradigm for spatial memory and to determine paralleling brain receptor complex levels. Sixty C57BL/6J mice were used in the study and divided into four groups (trained drug injected; trained vehicle injected; yoked drug injected; yoked vehicle injected). Animals obtained training for 4 days and were killed 6 h following the last training session on day 4. Hippocampi were dissected from the brain, membrane fractions were prepared by ultracentrifugation and were run on blue-native gels and immunoblotted with antibodies against major brain receptors. Modafinil treatment led to decreased latency and increased average speed, but not to changes in pathlength and number of correct decisions in the MTM. Drug effects were modifying receptor complexes of GluR1, GluR2, D2 and NR1. Training effects on receptor complex levels were observed for GluR3, D1 and nicotinic acetylcholine receptor alpha 7 (Nic7). GluR1 levels were correlating with GluR2 and D1 levels were correlating with D2 and NR1. Involvement of the glutamatergic, NMDA, dopaminergic and nicotinergic system in modafinil and memory training were herein described for the first time. A brain receptor complex pattern was revealed showing the concerted action following modafinil treatment.
    Amino Acids 05/2012; 43(6). DOI:10.1007/s00726-012-1306-y · 3.65 Impact Factor
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    ABSTRACT: In own previous work CD1 mice were tested in the Multiple T-maze (MTM), a robust land maze allowing determination of latency to reach the goal box with food reward and to evaluate correct decisions made on the way to the goal box. Herein, hippocampi of these animals were used for the current study with the aim to investigate differences in protein levels between trained and yoked mice and, moreover, to determine differences in protein levels between trained and yoked mice with and without memory formation in the MTM. Three training sessions were carried out for four training days each, followed by probe trials on Days 5 and 12. Good and no-performers in the MTM were separated based on means and median of latency to reach the goal box on probe trial Day 12. Six hours following the probe trial on Day 12, animals were sacrificed and hippocampi were taken. Proteins were extracted and run on two-dimensional gel electrophoresis, spots were quantified and differentially expressed proteins were identified by mass spectrometry using an ion trap. Levels of 17 proteins were significantly different in trained vs. yoked mice. Seven proteins were differentially expressed comparing trained vs. yoked mice from good and no-performers. A series of proteins were significantly correlated with latency and may link these proteins to spatial memory formation. Differential protein expression in trained vs. yoked mice and in good and no-performers may allow insight into spatial memory formation as well as represent tentative pharmacological targets.
    Hippocampus 05/2012; 22(5):1075-86. DOI:10.1002/hipo.20956 · 4.30 Impact Factor
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    ABSTRACT: Although a potential role for polyamines and transglutaminases (TGs) in memory mechanisms have been proposed, hippocampal spermine (SPM) and spermidine (SPD) levels as well as transamidating activity of TG in spatial memory have not been addressed yet. It was therefore the aim of the study to assess hippocampal polyamines and TG activity at the probe trial in a spatial memory paradigm. C57BL/6J mice (20 animals per group) were used for the experiments and divided into a trained and a yoked (untrained) group. The Morris water maze (MWM) was selected as the memory test, animals were sacrificed within 5 min following the probe trial and hippocampi were taken for biochemical analysis. SPD and SPM levels were assessed by an analytical procedure according to Gismondi et al. Transamidating activity of TG was determined following the method described by Chung and Folk using [14C] methylamine as substrate. γ-(Glutamyl)-polyamine levels were evaluated by ion exchange chromatography according to Folk et al. Animals learned the task in the MWM as latencies and pathlengths were significantly reduced. At the probe trial mice showed significantly higher preference for the target quadrant. Free SPD and SPM levels were manifold decreased in the trained as compared to the yoked group. Transamidating activity of TG was fourfold increased in trained as compared to yoked controls. γ-(Glutamyl)-SPD was comparable while γ-(glutamyl)-SPM was significantly higher in the trained group. The findings show a potential role for polyamines, their derivative γ-(glutamyl)-SPM and transamidating activity of TG at memory retrieval or formation. Results from this study are extending and knowledge on polyamines and report for the first time involvement of γ-(glutamyl)-SPM and transamidating activity of TG that may form the basis for future neurochemical and pharmacological studies and indeed, modulation of polyamine and TG activity has been already proposed as a tentative therapeutical concept.
    Hippocampus 05/2012; 22(5):1068-74. DOI:10.1002/hipo.22016 · 4.30 Impact Factor
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    ABSTRACT: Although the involvement of the mTOR (mammalian target of rapamycin) system in memory processes has been reported, information on the effect of rapamycin on spatial learning and memory is limited. It was therefore the aim of the study to show the effect of parenteral rapamycin administration to C57BL/6J mice on performance in the multiple T-maze (MTM) and to determine hippocampal mTOR activity. Rapamycin-treated and -untreated/trained/probed mice are the main part of the experiment considering retrieval and acquisition or consolidation of spatial memory. Six hours following euthanasia hippocampi were extirpated and used for evaluation of mTOR activity as represented by hippocampal levels of S6 protein and its phosphorylated active form (phospho S6 protein, S240,244), a read out of mTOR complex 1 activity. Mice given i.p. rapamycin learned the task of the MTM but failed at the probe trial, showing absence of the phosphorylated active form of S6 protein, indicating inhibition of mTOR activity. Herein, impairing effects of rapamycin on retrieval but not on acquisition or consolidation of spatial memory are shown. Deficient memory retrieval was paralleled by inhibition of mTOR complex 1 activity. The current study extends knowledge on rapamycin in memory mechanisms and challenges work on deeper insights into the role of mTOR in different phases of memory formation and retrieval.
    Behavioural brain research 04/2012; 229(2):320-4. DOI:10.1016/j.bbr.2012.01.017 · 3.39 Impact Factor
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    ABSTRACT: A series of individual proteins have been linked to performance in the Morris water maze (MWM) but no global effects have been reported. It was therefore the aim of the study to show which proteins were strain-independent, global factors for training in the MWM. Strains C57BL/6J, apodemus sylvaticus and PWD/PhJ were used. MWM and gels from trained animals were from a previous own study and corresponding yoked groups were generated. Hippocampal proteins were extracted and run on two-dimensional gel electrophoresis. Spots with different expressional levels between trained and yoked groups were punched and identified by mass spectrometry (nano-LC-ESI-MS/MS, ion trap). Two-way ANOVA with two factors (strain and training) was carried out and a Bonferroni test was used to compare groups. 12 proteins from several pathways and cascades showed different levels in trained mice versus corresponding yoked animals in all strains tested. Four out of these proteins were verified by immunoblotting: beta-synuclein, profilin 2, nucleoside diphosphate kinase A (NME1) and isocitrate dehydrogenase 3. Four proteins verified by immunoblotting could be shown to be involved in training in the MWM as a global effect, independent of the strain tested.
    Amino Acids 03/2012; 43(4):1739-49. DOI:10.1007/s00726-012-1258-2 · 3.65 Impact Factor
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    ABSTRACT: The NMDA receptor (NMDA-R) is a key element in neural transmission and mediating a vast variety of physiological and pathological processes in the nervous system. It is well-known that phosphorylation is required for functioning of the NMDA-R, and we therefore decided to study this post-translational modification in subunits NR1 and NR2A-D. Immunoprecipitation with an antibody against NR1 was carried out from rat hippocampi and SDS-PAGEs were run. Bands were punched, destained, and digested with trypsin and chymotrypsin and peptides were identified by nano-LC-ESI-MS/MS using an ion trap (HCT). Proteins were identified using specific software. Phosphorylations were verified by phosphatase treatment and reanalysis by mass spectrometry. The NMDA-R subunits NR1 and 2A-D were identified. On NR2A, a novel phosphorylation site was observed at S511, and on NR2B, four novel phosphorylation sites were revealed at S886, S917, S1303, and S1323 by mass spectrometry and verified by phosphatase treatment with mass spectrometrical reanalysis. A series of NMDA-R phosphorylations have been reported and these serve different functions as receptor activation, localization, and protein-protein interactions. Herein, findings of novel phosphorylation sites are extending knowledge on chemical characterization of the NMDA-R and warrant studying function of site-specific receptor phosphorylation in health and disease.
    Journal of Proteome Research 03/2012; 11(3):1891-6. DOI:10.1021/pr201099u · 5.00 Impact Factor

Publication Stats

3k Citations
641.85 Total Impact Points

Institutions

  • 2004–2015
    • Medical University of Vienna
      • • Department of Paediatrics and Adolescent Medicine
      • • Department of Biochemistry and Molecular Biology
      Wien, Vienna, Austria
  • 2006
    • Novo Nordisk
      København, Capital Region, Denmark
  • 2004–2005
    • IST Austria
      Klosterneuberg, Lower Austria, Austria
  • 1985–2005
    • University of Vienna
      • Department of Medicinal Chemistry
      Wien, Vienna, Austria
  • 2002
    • University of Nottingham
      Nottigham, England, United Kingdom
  • 1994
    • Heinrich-Heine-Universität Düsseldorf
      Düsseldorf, North Rhine-Westphalia, Germany